Remote terminal industrial control communication system

An industrial control system comprising:

• a communication network over which messages are exchanged between devices connected to the network with each device being assigned a network address, wherein each message contains a source address indicating the device from which the message originated and a destination address;
• a plurality of central processors each of which including means, coupled to said communication network, for the exchange of messages over the network, each of said central processors being assigned a unique address on said communication network;
• and
• a plurality of remote terminal units for exchanging messages with said central processor, each of said remote terminal units comprising:
• a) means, coupled to said communication network, for receiving messages,
• b) means for storing a first address and a second address;
• c) a first means for comparing the first address to the destination address contained in a message received from said communication network and producing a first indicia that the compared addresses are the same,
• d) a second means for comparing the second address to the source address contained in the message received from said communication network and producing a second indicia that the addresses compared by said second means are the same, and
• e) means for responding to the received message in response to the presence of both the first and second indicia.

A remote terminal unit, for an industrial control system that includes a communication network for the exchange of messages in which each message contains a destination address and a source address, a central processor which executes a control program to operate equipment connected to the industrial control system and which is coupled to the communication network, wherein the remote terminal unit comprises:

• means, coupled to said communication network, for receiving messages from the central processor;
• means for storing a first address and a second address;
• a first means for comparing the first address to the destination address contained in a message received from said communication network and producing a first indicia that the compared addresses are the same;
• a second means for comparing the second address to the source address contained in the message received from said communication network and producing a second indicia that the addresses compared by said second means are the same;
• and
• means for responding to the received message in response to the presence of both the first and second indicia.